Machine for cutting curved, selfconjugate indentations



-Alfig. 2% 1946. I A .FOR$TER 2,40%,609

MACHINE FOR CUTTING CURVED SELFCONJUGATE INDENTATIONS v Filed Aug. 23, 1940 3 Sheets-$hee t 1 Aug. 2Q, 1460 A. FORSTER 2,405,009

I MACHINE FOR CUTTING CURVED SELFCQNJUGATE INDENTAIYIONS Filed Au 23, 1940 s Sheps-Sheet} I 75 I u" r v Invent r;-

and the axes of rotation of the milling heads are Patented Aug. 20, 1946 MACHINE FOR CUTTING CURVED, SELF- CONJUGATE INDENTATIONS Albert Forster, Milanino, Italy, assig nor to .Buhler Brothers, Uzwil, Switzerland, a corporation of Switzerland Application August 23, 1940, Serial No. In Switzerland August 24, 1939 16 Claims.

1 The present invention relates to a machine for cutting curved, selfconjugate indentations by continuous rolling. Hereinafter there will be called selfconjugate such identations which are able to mesh with congruous identations and the 5 teeth will be called curved when their axes, lying on the pitch surface, have a longitudinal curvature. In an indentation one will consider the number of teeth z and the pitch t and with redisplaced with regard to one another by a given distance in the direction of the axis of rotation of the blank. The speeds of translation 11 and 112 may have any value, but the quickest cutting of an indentation is obtained, under same. circumstances, when 12 and w are equally great, but have the opposite sign (w=v). The ratio between the speeds of rotation of the milling heads is, in this case:

gard to the milling heads cutting the concave or i iv z w V convex faces of teeth one considers the speeds g tzv tz+w of rotation f and g of the Cutting motions as Well This ratio results generally out of one or more as the speeds of translation 17 and w of the feedrather great prime numbers so that for carrying ing motions. A feeding motion will be regarded it out in practice one must gear wheels with aspositive (negative) when ithasapositive(negamany hundreds of teeth The gearings Carma tlve) moment about P axls. of P ing out these ratios must however also permit the Methods and machlnes for cuttmg these kmd of variation of the ratio itself, i. e. they must be indentations are known and use at least two millprovided with change wheels, in order to cut on ing heads rotating about their Own axis (cutting the machine indentations with various numbers movement) and at the same time translating at 20 of teeth right angles to their own axis and to that of the In. addition thereto these gearings must, eSDeblank (feeding movement) Whilst the blank also cially for the transmission of the cutting motion rotates about its oWnaxis, as well for effecting the to the mining heads, t n f the Whole cutting rolling as for generating the longitudinal curvaenergy so that the change wheels must have a tllre of teeth. For practically Various corresponding great rnodulus Many teeth and a Cutting a feeding speeds of the milling heads great modulus require however great dimensions gearings are commonly used, whose toothed gears of t hange Wheels a of t change peed have numbers of teeth such that the require gear. ratios of t a s ssio are o t The machine for carrying out the method ac- Ratios between th spee of r t n of 3 cording to the invention overcomes these diflicultranslation of the milling heads are known, being ti by using a planetary gear connecting the such that the speeds of rotation of the milling hafts which impress the cutting or feeding moheads cutting the concave and convex tooth faces tion to the milling heads cutting the concave and are different from one another and their speeds to those cutting the convex faces of teeth and of translation may also be uneven. adapted to superimpose to the driving motion with With known methods and machines, having so relatively great speed of rotation and working defined cutting and feeding speeds selfconjugated energy a subsidiary controlling motion with relindentations cannot be cut in perfectly correct atively small speed of rotation and correspondmanner, since the curvatures of the concave and ingly low controlling energy. The controlling moconvex tooth faces do thereby not in all cases 40 tion may be picked up from a change speed gear result exactly equal, so that the indentations do of the machine or from a link of the mechanism not perfectly mesh with each other. transmitting the-motion to a feeding screw. The The object of the invention is a machine for planetary gear may be preceded by a worm gear cutting such indentations, with which in any case and a part of the change speed gear may be built exactly equal profiles and longitudinal curvaitse f as a p a etary e rccordin to an emtures are obtained and therefore selfconjugate bod ent O t n on t e p t y a may indentations meshing with each other with abbe inserted between the feeding screws and a solute perfection may be cut. gearing having one or more fixed transmission I carrying t t invention, th ti ratios may be provided between the shafts of the tween the speeds of rotation of the milling heads milling heads- According to a oth r embodiis made ment, which may use equally great feeds for both milling heads, the planetary gear may be inserted g between the shafts of the milling heads. The

source of energy may be applied so that the planetary gear lies within the flow of energy either to blank axis, parallel to the blank axis, slidable' carriages for the milling heads may beprovided.

The appended drawings are diagrammatical views of a machine for carryingfoutthepiethod according to the invention shown in some'embodiments given merely as examples, and precisely: I

The Figure 1 is a sectional elevation of aifirst embodiment; w

The Figure 2 is a plan view of a sec'ond'embodiment;

' The Figuresis ,a-plan viewof-athirdembodiment.

"Many other embodiments are however possible within the invention.

' Referring to the figures; the blank'l is fixed on a' rotatable, horizontal work table 2, carrying anindex'wormwlieelt, whichis'driven by a worm 4 receiving the'motion "through shaft :5, bevels B and shaft 1 from the cha nge"spee'd gear 8 of the machine Thelmilling heads ll, 2i are journalled on vertically "slidable carriages I2, 22 and these carriagesare'.carried.by slides I3, 23 which may slide horizontally along; guide ways 90, 92 and EH, 93.f1xed on.the mainframe-gill!) of 'the machine. The slides: I3, 23 are longitudinally driven.by;feeding"screws.; I4, for effecting the feeding motion of the milling-heads. ,These feeding :screws are .driven ibysha'fts 64, 114, worm wheels 65, '15, worms ;6'!, Hand shaft fiii from the change speed gear 82 of the machine. The changeispeed gear \82 :receives .motion from a shaft 59 driven by the change speed gearBl of themachine. xThe milling heads I LL21 are keyed I6, 26 in order to avoid'ivibrations and'are driven from the transmission shafts 3l,.4l which. are connected with the main'change speed geari34, driven by the source of energy 35 through-bevel gearsu32, 42 and shaft's33, 43. The change speed 'gearsB and 8| are also'in'driving relation with the same source of..energy-'35.'

According to Figure l the change speed gears 8 and 8! are connected through bevels 43"with theshaft-43. The shaft 66 is driven from the change speed gear 82 through a'bevel gear'fiii'.

The shafts I5, 25 of the millingheadsare connected with the transmission'shaft's 31, 4| through spur gears ll, 21, bevel gea'rs l8.-28, vertical shafts [9, Hand bevelgears 2 0,-40. The main change speed gear 34 drives shaft 33.

The shafts l5, 250f the milling heads ll, 2! are displaced with regard-to one another by the distance S in the direotionof the axis of rotation of "the blank I. This'dist'ance is defined as the distanceof the planes parallel to thework table '2 and'passing through the axes of the shafts l5 and 25 of the milling heads. The distance S is afunction of the width and of the modulus of the indentation to'be cutandofthe radius of the milling headsgmeasured at the cutting edges of the'cutters and iit isindepen'dent from the number of teeth. The distances-remains thus invariatedwhen cutting a wheel and successivelycutting the corresponding pinion,' so that errors of position ofthe axes'of the milling heads are avoided and perfect relationship of the curvatures of teeth is assured. The amount of this distance S may however be chosen at will, without preventing the machine from cutting correct selfconjugate gears.

The toothed gears carrying out the ratio according to the inventionbetween the speeds of rotation of the milling heads are provided at two places: between shafts 33 and 43 there are the spur wheelgear 31 with one fixed ratio and thelplanetary gear 44, which is connected with the foregoing through a shaft 38 and receives the controlling jmOtiOn from the shaft 59 through ohange-speedigear 83 and worm gear 46, 45; before the feeding screw 24 there is the planetary gear 54,-which receives the controlling motion,

"through the control worm 5B and the shaft 51, if also-from the shaft 59.

.on rotatable shafts 15,125 whichca'rry. flywheels 7 With this machine, in order to obtain the correct ratio tz+v according to the inventionbetween the speeds of rotation of the millingheads and their speeds of translation, either thegearing 31 with fixed ratio or the planetary gears "44 and "54 maybe conveniently chosen-whilst a variation of this ratio is obtained by means of the control change speed gear 83, which has to'deal only with the small control energy *and therefore may have small overall dimensions'and little weight. This machine may'therefor'e' cut any type of indentations, as well those for which w=v (in which case thefeeding screws l4 and 24 have equal great speeds of rotation and the control worm 56 remains fixed), as those for'which w and v are in any other ratio to one another.

According to this embodiment the fixed gear 31 and the'planetary gear 44 are situated in the transmission of motion between the external source of energy 35 and the blank l, the shaft 25 and both feedingyscrews I4, 24 as well'as the derivation of the-control motion for both planetary gears 44'and 54, whilst the planetary gear 54 is situated outwards of the transmission of motion from the same source'of energy 35 w the blank and the shafts of the milling heads. The flow of energy to the blank, the shaft 25 and thescrew l4 passes therefore through the gear 44, but not through the gear 54.

The source of energy 35 couldhowever'also be located at any Oth61 'Sil3B, e. g at the shaft 29 or '51, and the gearings31 and 44 would then no more be within the,v flow of energy to the blank, the shaft 25 and-the feeding screws, but only within that to the, shaft l5. Further; instead of,

or in addition to; a change speed gear 83, for the-transmission of the control motion to the planetarygear 44 or 54, another planetary gear could also be used.

According to Figure 2, the machine is provided with three milling heads H, 2|, m. The milling "head l2l"assiststhe milling head 2i in 'cutting'the convex faces of teeth on the blank I and permits a greater production to be obtained from the machine, without touching anything at the milling head I l The milling .head'l2l is journalledsimilarly toboth other milling heads onavertically displaceable "carriage l22, which may be displaced along the guide way I9! by means of a slide I23 ancliafeeding screw I 24, which is moved by the screw 24 through a bevel gear I84. The milling head [2| is keyed ona rotatable shaft l25'provi'ded with a fiywheel'lZG and driven from the transmission shaft l Ml; which is connected with the shaft 43 through a bevel gear I42. The milling head I2l has alspeed of rotation and a speed of translation as great as those of themilling head 2|; the direction of these speeds ishowever different, since the milling head 12! has another angular-position about the blank. The milling head l2l is displaced, equally as the milling head 2|, with regard to the milling head I l, by the above defined distance S in the direction of the blank axis.

In this machine the main change speed gear 34 drives directly the shaft 43 and the shaft 3!, which is connected with the foregoing one, drives through a bevel gear 132 the shaft 36, which is connected through bevels 36' with the change speed gears 8 and 8|. The change speed gear 82 is connected with the shaft 66 through bevels 66C. The milling heads 15, 25, I25 are connected through spur gears I1, 27, I21, bevel gears I8, 28, I28, vertical shafts i9, 29, I29 and bevel gears 20, 40, I40 with'the transmission shafts 3|, 4!, MI. 7

For setting the correct transmission ratio between the speeds of rotation and of translation of the milling heads cutting the concave and those cutting the convex faces of teeth, a change speed gear 310. with training wheels l0 giving two fixed ratios is provided between the shafts 33 and 43, and a planetary gear 54 is provided before the feeding shaft M andcontrolled, through a worm gear 55, 56, shaft 51 and bevel gear 58, from the shaft 59.

According to this embodiment the planetary gear 54 is out of the flow of energy from the external source of energy to the blank and the shafts of the milling heads. The gearing 31a is on the contrary within the flow of energy as well to the blank and the feeding screws as to the shaft [5. It is understood that-the milling head II also could be doubled, or any milling head could be assisted by two or more others.

According to Figure 3 the main change speed gear 34 drives the shaft 3i, which in turn drives through bevels I32, shaft 36 and bevels 36 the change speed gears 8 and 8|. Between shaft 59 and change speed gear 82 bevel wheels 60 are provided. The shafts I5, 25 are driven by shafts 3|, 4| by means of bevel gears 3 la, Ma.

According to this embodiment only two milling heads are provided, which have equally great, but contrary feeding speeds. The feeding screws are therefore driven with equally great speeds of revolution. The planetary gear 44 serving for carrying out the ratio according to the invention between the speeds of rotation of the milling heads is inserted between the shafts 33 and 33 and is controlled by shaft 59 through worm 36 acting upon its casing 49, which is formed as a worm wheel.

On this machine the axes of the milling heads are parallel to one another and the carriages thereof could therefore be fixed on the main frame of the machine, whilst the feed would be effected by the blank. The feeds of both milling heads have indeed the same direction in the space and the same value, so that the carriages are immovable to one another and move themselves only with regard to the blank.

On this embodiment the planetary gear is out of the flow of energy from the source of energy 35 to the blank I, to the shaft I5, to the feeding screws and to the derivation of ,the controlling motion for the planetary gear itself. The source of energy could however also, be located at anyoth'er place, e. g. on the? shaft 4!, so that the planetary gear would be'within the flow of energyto all the above'named points of utilisation.

"In the various embodiments of the machine according .to the invention the planetary gears andthe change gears with fixed transmission ratios may be as well made with bevel as with hypoid or spur toothed wheels, or with chain or worm gears, etc. and they may have any trans-' mission ratio. The change speed and other gearings may be made and disposed in any manner other than shown and described. The planetary gears may be inserted either in the transmission of the cutting motion (rotation) or in that of the feeding motion (translation) to one or more milling heads; a, planetary gear may be inserted also in the transmission of the rotating or translating movement to theblank and used as well alone as in addition to another transmission gear of known construction. The milling heads may be used in any quantity and rotate either in the same or in opposite senses and they may have any angular position about the blank. Either a single or a plurality of, conveniently synchronised, sources of energy, either electric or pneumatic, hydraulic, thermic, or purely mechanic may be used for the various drives. Several other particulars may also be executed in various manners within the limits of the appended claims.

I claim:

1. A machine for cutting self-conjugated curved indentations by continuous rolling, comprising a work table, adapted to carry a blank and having an axis of rotation, a milling head, adapted to cut the concave faces of teeth, operatively connected with said Work table, having an axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a, feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, another milling head, adapted to cut the convex faces of teeth, having an axis of rotation and elfecting'a cutting motion consisting'of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, means, operatively connecting the said milling heads and adapted to impress on said second mentioned milling head a driving motion of great speed and energy and a. superimposed, variable, control motion of little speed and energy, carriages, slidable in a direction parallel to the said axis of rotation of the work table, adapted to carry the said milling heads and to displace same with regard to one another.

2. A machine for cutting self-conjugated curved indentations by continuous rolling, comprising a work table, adapted to carry a blank and having an axis of rotation, a milling head, adapted to cut the convex faces of teeth, operatively connected with said work table, having an axis of rotation and effecting a cutting motion .consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and. of said work table, another milling head, adapted to cut the concave faces of teeth, having an axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, means, operatively connecting the said; milling. :heads; and :adaptedito impress on said second. mentioned milling head a driving motion of greatspeed and: energy and a superimposed; variable, controlimotion of little speed and energy, carriages-"slidable in a directioniparallel to thesaid axis of rotation: of the work table, adapted 1 to 'carry the .said. milling heads .and to displace. same with regard toone another.

3. A machine for cutting. self-@conjugated curved indentations by continuous rolling, :comprising a work table, adapted to carry. a blank and'having-an axis of rotation, a milling. head, adapted to cut the concave faces of teeth, being operatively connected with said work table-,hav ingan. axis of rotation and efiectingza cutting motion consisting of a rotation about: the said own: axis and a'feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of saidwork table, another millinghead, adapted. to cut the convex faces of teeth, having an axis of rotation and effecting. a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translationin a direction at right angles to the said axes of rotation'of its own and of said work table, a planetary gear, operatively connected to said milling heads and adapted, to impress on said second mentioned milling head a feeding motion consisting of a driving motion of great speed and energy and a superimposed, variable, control motion of little speed and energy, a gearing with a fixed transmission ratio, operatively connecting the said milling heads and adapted to impress on said second mentioned milling head a cutting motion consisting of a rotation at a speed being in a given ratio to the speed of rotation of said first mentioned milling head, carriages slidable in a direction parallel to said axis of rotationof the work table, adapted to carry the said milling headsand to displace same with regard to one another. I I

4. A machine for cutting self-conjugated curved indentations by continuous rolling, comprising a work table, adapted to carry a blank and having an axis of rotation, a milling head, adapted to cut the convex faces of teeth, being operatively connected with said work table, having an axis of rotation and effectinga cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of the said work tablaanother milling head, adaptedlto cut the concave faces of teeth,having an axis of rotation and efiecting a cutting motion consisting of a rotation about the-said ownaxis and a feeding. motion consisting of a translationin a direction. at rightangles to the said axes of rotation of its own and of said work table,-. a planetary, gear, operatively connected to said milling heads and adapted to impress on said second mentioned milling head a feeding motion consisting of a driving motion of great speed and energy and a superimposed, variable, control motion of little speed and energy, a gearing with a fixed transmission ratio, operatively-connecting the, said milling heads and adapted to impress on said second mentioned milling head a cuttingmotion consisting of a rotation at a 'speed being in a given ratio to the speed of rotationof said first mentioned milling head, carriages: slidable: in, a direction parallel to-- said axis of? rotation; of the work table, adapted to carry thesaidt milling.

heads .and to; displace same with regard" to one another.

5. Av machine. for cutting self-conjugated curved indentations by continuous rolling, comprisinga work table, adapted to carry a-blank and havingzan axis of rotation, a milling head, adapted to cut the concave facesof teeth, being operatively connected with-said work table, having; an axis of rotation and eifectinga cutting motion consisting, of a rotation about the. said own axis and a feeding motion consisting of a translation in a direction-at right angles to the said axes of rotation of its own and of said work table, another'milling head, adapted: to cut the convex faces ofteeth, having an axis of rotation and effecting a cutting motion consisting of a rotationjaboutthe said own axis and a feeding motionconsisting ofa translation in a direction at right angles to the said axes of rotation of its own and of said work table, a planetary gear, operatively connected to said milling heads and adapted to impress on said second mentioned milling head a feeding motion consisting of a driving motion of great speed and energy and a superimposed, variable, control motion of'little speed and energy, a gearing with'a plurality of fixed transmission ratios, operatively connecting the said milling heads and adapted to impress on said second mentioned milling head a cutting motion consisting of a rotation at a speed being in a given ratio to the speed of rotation of said first mentioned milling, head, carriages slidable in a direction parallel to said axis of'rotation of the work table, adapted to carry the said milling heads and to displace same with regard to one another.

6. A machine for cutting self-conjugated curved indentations by continuous rolling, comprising a work table, adapted to; carry a'blank and having an axis'of rotation, a milling head, adapted tocut the convex faces of teeth, being operatively connected with said work table, having an; axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting'of a translation in a direction at right anglesito the saidaxes of rotation of its own and of said work table, another milling head, adaptedtocut the concave faces of teeth, having an axis of rotation and effecting a cutting motion consisting ,of a rotation about the said own axis and afeeding motion consistingof a, translation inadirection at right angles to the said axes of rotation of its own and of the said work table, a planetary gear, operatively connected to said milling heads and adapted to impress. on said second. mentioned milling head, a feeding motion consisting of a driving; motion of great speed and energy and a superimposed, variable, control motion of little speed and energy, a gearing with a plurality of fixed, transmission ratios, operatively connecting the said millingheadssand adapted to impress on said second mentioned milling head a cut ting motion consisting of a rotation at a speed being ina given ratio to the speed of rotation of said firstmentioned milling. head, carriages slidable in.ai'directionparallel to said axis of rotatiorrof the worktable, adapted to carry the said milling heads and to displace same :with regard to oneanother.

7; Amachine for cutting selfconjugated-curved indentations by continuous rolling, comprising a Worketable, adapted to carry a-blank and having an. axis? of rotation, a milling head adapted to cut; the concave faces of teeth,operatively connected with said workitable', having an axis of'rotion at right angles to the said axes of rotation of its own and of said work table, another milling head, adapted to out the convex faces of teeth, having an axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, a planetary gear operatively connected to said milling heads and adapted to impress on said second mentioned milling head a cutting motion consisting of a driving motion of great speed and energy and a superimposed, variable, control motion of little speed and energy, carriages, slidable in a direction parallel to the said axis of rotation of the work table, adapted to carry the said milling heads and to displace same with regard to one another.

8. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table, adapted to carry a blank and having an axis of rotation, a milling head, adapted to cut the convex faces of teeth, operatively connected with said work table, having an axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, another milling head, adapted to cut the concave faces of teeth, having an axis of rotation and effecting a cutting motion consisting of a rotation about the said own axis and a feeding motion consisting of a translation in a direction at right angles to the said axes of rotation of its own and of said work table, a planetary gear operatively connected to said milling heads and adapted to impress on said second mentioned milling head a cutting motion consisting of a driving motion of great speed and .energy and a superimposed, variable, control motion of little speed and energy, carriages, slidable in a direction parallel to the said axis of. rotation of the work table, adapted to carry the said milling heads and to displace same with regard to one another.

9. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table, a milling head, adapted to cut a face of the teeth, means operatively connecting said milling head with said work table, another milling head, adapted to cut the opposite face of the teeth, a planetary gear operatively connected with said above mentioned means, other means operatively connecting said planetary gear with said second mentioned milling head, a change speed gear, operatively connected with said work table and adapted to impress a control motion on said planetary gear, a source of energy, adapted to drive said work table and said milling heads, being operatively connected with said first mentioned means.

10. A machine for cutting self conjugated curved indentations by continuous rolling, comprising a work table, a milling head, adapted to cut a face of the teeth, means operatively connecting said milling head With said work table, another mill ing head, adapted to cut the opposite face of the teeth, a planetary gear, operatively connected with said abovementioned means. other means, operatively connecting said planetary gear with said second mentioned milling head, a change 10 speed gear, operatively connected with said work table and. adapted to'impress a control motion on said planetarygear, a source of energy, adapted to drive said work table and said milling heads, being operatively connected with said second mentioned means.

'11.'A machine for cutting s'elfconjugated curved indentations by continuous rolling, comprising a work table, a milling head, adapted to cut a face of the teeth and operatively connected with said work table, another milling head, adapted to cut the opposite face of the teeth, a planetary gear comprising bevel wheels and operatively connecting said milling heads, and a change speed gear, operatively connected with said work table and adapted to impress a control motion on said planetary gear.

12. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table,a milling head, adapted to cut a face of the teeth and operatively connected with said work table, another milling head, adapted to cut the opposite face of the teeth, a planetary gear operatively connecting said milling heads, and a change speed gear, operatively connected with said work table and adapted to impress a control motion on said planetary gear.

13. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table, a milling head, adapted to cut a face of the teeth and operatively connected with said work table, another milling head, adapted to cut the opposite face of the teeth, a planetary gear operatively connecting said milling heads, a change speed gear, operatively connected with said work table, and a worm gear driven by said change speed gear and adapted to impress a control motion on said planetary gear.

14. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table, a milling head, adapted to cut a face of the teeth and operatively connected with said work table, another milling head, adapted to cut the opposite face of the teeth, a planetary gear, operatively connecting said milling heads, a pair of slides, adapted to carry said milling heads and to slide across the blank, a pair of feeding screws, operatively connected with said work table and adapted to drive said slides for impressing a feeding motion on said milling heads, and means, operatively connected with a said feeding screw and adapted to impress a control motion on said planetary gear.

15. A machine for cutting selfconjugated curved indentations by continuous rolling, comprising a work table adapted to carry a blank and having an axis of rotation, a pair of milling heads, having parallel axes of rotation and each adapted to cut a face of teeth on the said blank, slides movable in a direction at right angles to the axes of rotation of the said Work table and carrying said milling heads, a planetary gear means operatively connecting said planetary gear and said milling heads, a source of energy operatively connected with said means, and means, operatively connected with said source of energy and adapted to impress a rotation on said work table and to impress a control motion on said planetary gear.

16. A machine for cutting selfconjugatcd curved indentations by continuous rolling, comprising a work table adapted to carry a blank and having an axis of rotation, a pair of milling heads, having parallel axes of rotation and each adapted to cut a face of teeth on the said blank, a carriage, adapted.torcarry'asaidemilling head and..- to be' displaced in a directionparallel to said axis.- of rotation of the saidwork-table;1movab1e=-in a-= direction at rightangles to:-the;1axes of rotation of the said work-tableandcarrying zsaidmilling heads, a planetary gear, means operatively-con-- necting said planetary gear and said milling gear;-

ALBERT FORSTER; 

